Targets, such as areas where optically transduced chemical and/or biochemical assays are performed, may need to be illuminated by a light source. It is often desirable to illuminate the target with light having enhanced uniformity of intensity over the entire target region. Optical signals are typically a function of the illumination intensity and, the more an illumination intensity varies across a target, the more the optical signal will also vary. The resultant variance in optical signals may be undesirable.
However, it can be difficult to efficiently provide illumination having enhanced or a high degree of uniformity. For example, lasers, which are commonly used for illuminating targets, typically have an intensity profile that is peaked at its center and which drops off radially towards the edges. This intensity profile is often a Gaussian, or bell shaped, profile. Therefore, if a target is directly illuminated with such a laser, the illumination of the target will not have a constant intensity. Rather, the center portion of the target will receive greater illumination intensity than the perimeter areas.
Therefore, there is a need for an apparatus and method to illuminate a target or selected area with enhanced uniformity as compared to directly illuminating the target with a given light source. Further, there is a need for an apparatus and method that provides enhanced illumination uniformity for optical targets such as those in chemical and/or biochemical assay systems.